The theory divides the way people attribute causes to events into two types. External attribution assigns causality to an outside factor, such as the weather, whereas internal attribution assigns causality to factors within the person, such as their own level of intelligence or other variables that make the individual responsible for the event. People are more likely to make internal attributions when the event is positive, and external ones for negative ones.
Through a self-fulfilling prophecy, the attribution of events can change a person's behaviour. This fact has been used to develop methods of behaviour modification. The theory predicts that there may be negative effects to using external rewards or punishments in behaviour modification. External results prevent people making an internal attribution, and thereby makes them feel less responsible for their own behaviour. They believe the external factor is actually causing their behaviour. For example, if someone is paid for a job, they attribute the fact they are doing the job to the fact they are making money for it, rather than to intrinsic factors, such as enjoyment. External rewards, such as payment, can change the way a person behaves. Studies have shown that adding an external reward to a task previously rewarded only internally makes people less intrinsically motivated to perform that task.
However, in some circumstances, extrinsic factors can cause positive changes in behaviour. If an individual believes that they have earned the reward or punishment for intrinsic reasons, then that might effect a positive change in behaviour. It is when the reason for the reward is attributed to external factors that the behaviour change might not be in the desired direction.